Toward Polymer Solar Cells:rational Design, Synthesis,and Photovoltaic Effect In Low Bandgap Polymers

Polymer photovoltaic cells have been an efficient means to harvest solar energy,When it comes to low-bandgap polymers, many methods such as side-chain engineering、energy level modulation and expanding conjugation degree have been used to enhance the result of related devices.In detail, the paper is focused on low-bandgap polymers and photovoltaic properties, and devided into six chapters.In chapter 1, The backgroud and development of polymer photovoltaic cells are introduced in detail. Next, the development of typical solar cell stucture and some conjugated polymers have been introduced. Lastly, the design ideas of the materials and the main reserch work of this paper have been discussed.In chapter 2, Coupling with a new accepter units phenanthrenequinoxaline and benzo[1,2-b:3,4-b′]dithiophene(BDT) to get the polymer PBDTFPQ. Rational absorption and good thermal stability have been discussed, the ralated divice got a resonable PCE, which is a better candidate for polymer donor.In chapter 3, PC16BDTT-T-FPQ、PC8BDTT-T-FPQ and PBDT-T-FPQ are obtained after using fluorinated phenanthrenequinoxaline derivatives as acceptor and different BDT units with different side-chains as donor. The research work focused on the side-chain effect of BDT units, especially on the photovoltaic properties; the absorption spectra of polymers have shown diverse, PC16BDTT-T-FPQ and PC8BDTT-T-FPQ, which contains two-dimensional conjugated benzodithiophene units, have a broader absorption spectra than PBDT-T-FPQ. The polymer PC16BDTT-T-FPQ contains 2,3-dioctylthiophene side chain in the BDT unit possesses deeper HOMO energy level than the another two polymers.In chapter 4, Four polymers, IDT-T-FPQ 、 IDT-FPQ(W/O) 、 PIDT-FPQ and PIDT-DFPQ are discussed by coupling with fluorinated phenanthrenequinoxaline derivatives as acceptor and Indacenodithiophene(IDT) as donor. The HOMO level and absorption spectra of the polymes is consistent with the number of fluorine atoms.In chaper 5, Two polymers FPQ and FTQ have been synthesized. The UVabsorption、electrochemical and HOMO energy level have been discussed after the conjugation degree expanded. A higher PCE of 5.77% is obtained when it comes to FPQ device.In chapter 6, The summary of my research work, outlook of my team research on OPV in the future.